# NTSB LAX02LA121: Rotorway Exec 165F, N21901, Chandler, AZ, April 1, 2002 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: April 1, 2002, 09:55 local (16:55 UTC) - Place: Chandler, AZ - Coordinates: 33.269165, -111.811111 - Nearby events: https://openairdocs.org/map.md?lat=33.2692&lon=-111.8111&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: Serious injuries - Injuries: 1 serious, 1 minor - Status: Completed, report February 5, 2004 - Report: Approved by Office Director - Parties: Federal Aviation Inspector - NTSB case key (mKey): 54436 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX02LA121 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/54436/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=54436 - Page: https://openairdocs.org/ntsb/LAX02LA121 ## Probable cause The tail rotor drive system failure as a result of incorrect installation procedures by the manufacturer's personnel. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, approach - vfr pattern - final approach - maintenance,installation - improper, manufacturer (cause) - rotor drive system,tail rotor drive shaft - failure (cause) - Loss of control - in flight, approach - vfr pattern - final approach - tail rotor/anti-torque control - not available (cause) - directional control - not possible, pilot in command - In flight collision with terrain/water, descent - uncontrolled - terrain condition - ground ## Analysis The helicopter collided with the ground following a loss of tail rotor drive during a steep approach. After performing various maneuvers, the certified flight instructor (CFI) and the student began traffic patterns to a landing zone (LZ). On short final, approximately 40 feet agl, and 40 mph, the helicopter yawed left slowly. When the helicopter had reached a 45-degree left yaw, the CFI took the controls. As the helicopter approached a 90-degree left yaw, the CFI had applied full right pedal. Simultaneously, he lowered the collective and reduced power. The helicopter rotated 360 degrees about 3 times before impact. Post accident inspection revealed incorrect installation of the forward end of the intermediate drive belt on the intermediate pulley group. The tail rotor drive system uses three belts, interconnected via pulleys at various points within the tail boom, to drive the tail rotor. The forward and aft belts and pulleys were normal. The intermediate belt was found shredded, burned, and separated. The aft end of the intermediate belt was positioned correctly on the rear pulley; however, the forward end was around the wrong pulley, the one meant for the forward belt, which induced a large misalignment of the intermediate belt and consequent rub between it and the pulley side. All pulleys were installed with specified tightness and with fore/aft play as stated in the maintenance manual. Maintenance records for the helicopter indicated that the belts were replaced twice in the past 8 months, both times by the manufacturer. The first time was in August 2001, for a heavy maintenance rebuild. The second time was in November 2001 following a tail rotor strike. The belts had about 200 hours operating time since their last replacement in November. ## Factual narrative On April 1, 2002, at 0955 mountain standard time, a Rotorway Exec 165F helicopter, N21901, collided with the ground following a loss of tail rotor drive during a steep approach near Chandler, Arizona. The helicopter, owned and operated by Rotorway International under 14 CFR Part 91, was on a local area instructional flight. The helicopter sustained substantial damage. The commercial pilot/flight instructor sustained serious injuries, and an airline transport pilot student sustained minor injuries. Visual meteorological conditions prevailed and no flight plan was filed. The flight departed from Stellar Airpark, Chandler, about 0900. The CFI reported that after performing various maneuvers, he and the student began traffic patterns to a landing zone (LZ). On short final, approximately 40 feet, and 40 miles per hour (mph), the helicopter yawed left slowly. When the helicopter had reached a 45-degree left yaw, the CFI took the controls. As the helicopter approached a 90-degree left yaw, the CFI had applied full right pedal. Simultaneously, he lowered the collective and reduced power. The helicopter rotated 360 degrees about 3 times before impact. The helicopter impacted the ground, collapsing the right skid, and coming to rest on its right side. The helicopter was examined at Rotorway International in Chandler under the auspices of the Federal Aviation Administration (FAA) inspector. He reported that the tail rotor drive system uses three belts, interconnected via pulleys at various points within the tail boom, to drive the tail rotor. The forward and aft belts and pulleys were normal. The intermediate belt was found shredded, burned, and separated. The aft end of the intermediate belt was positioned correctly on the rear pulley; however, the forward end was around the wrong pulley, the one meant for the forward belt, which induced a large misalignment of the belt and consequent rub between it and the pulley side. All pulleys were installed with specified tightness and with fore/aft play as stated in the maintenance manual. The engine, clutch, drive belt system, and transmission were found in working order. Maintenance records for the helicopter indicated that the belts were replaced twice in the past 8 months. The first time was in August 2001, for a heavy maintenance rebuild. The second time was in November 2001 following a tail rotor strike. The belts had about 200 hours operating time since their last replacement in November. On April 4, 2002, Rotorway International issued a Mandatory Compliance Bulletin M-20 that required immediate inspection to verify proper routing of tail rotor drive belts through the tail boom. Any belt not properly routed into the correct idler pulley groove required immediate replacement. ## Aircraft - Registration: [N21901](https://openairdocs.org/deregistered/N21901-2003-11-12), registration cancelled 2003-11-12, S/N RI6035, built 1995 (OpenAirDocs) - Reported make and model: Rotorway Exec 165F - Registry model: [Cobb Intl Inc/DBA Rotorway INT EXEC 162F](https://openairdocs.org/model/cobb-intl-inc-dba-rotorway-int-exec-162f) (registry code 05625SN) (OpenAirDocs) - Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs) - Category: Helicopter - Serial number: 6035 - Airframe hours: 1776 - Engines: Rotorway 162F 150 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Registered owner: Cobb International, Inc. - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Continuous airworthiness, March 18, 2002, 12 hours before - Departed: P19, Chandler, AZ ## Flight crew As NTSB recorded them. NTSB leaves out names. - Flight instructor; age 47; injuries: serious; flight instructor, commercial; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 2, valid medical--w/ waivers/lim; last flight review April 30, 2000; seat: right; flight hours: 1,600 total, 800 in this make and model, 1,500 as pilot in command - Student pilot; age 55; injuries: minor; flight engineer, flight instructor, airline transport, commercial; airplane ratings: single-engine land, multi-engine land, single-engine sea; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; last flight review November 17, 2001; seat: left; flight hours: 17,000 total, 1 in this make and model, 13,000 as pilot in command, 180 in the last 90 days, 60 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 0° at 0 knots - Visibility: 35 statute miles - Lowest ceiling: none - Temperature: 73 °F, dew point 34 °F - Altimeter: 29.87 inHg - Observed at: KCHD, 8 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20020401005029A](https://openairdocs.org/incident/20020401005029A), Apr 1, 2002: Amtr EXEC162F, Chandler, AZ, No damage. (-23) The ip & student were conducting a "transition" training flt. Southeast of stellar airpark (P19). While practicing a short final approach onto a remote… ## Other investigations on N21901 (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB LAX00LA173](https://openairdocs.org/ntsb/LAX00LA173), Apr 6, 2000: Rotorway Exec 162F (N21901), Chandler, AZ, substantial damage. Probable cause: The inadequate maintenance inspection of the secondary shaft which resulted in its fatigue failure that emanated from a corroded circumferential score mark. A factor was the fence that the pilot… ## Docket (8 files) The files NTSB released with the investigation on November 25, 2003, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=54436. 1.4 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 428 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40422548&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Logbook and Maintenance Excerpts (item 2, .PDF, 334 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40185040&FileExtension=.PDF&FileName=Logbook%20and%20Maintenance%20Excerpts%0D%0A-Master.PDF - Record of Conversation FAA (item 3, .PDF, 31 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40185042&FileExtension=.PDF&FileName=Record%20of%20Conversation%20FAA%0D%0A-Master.PDF - Record of Conversation Rotorway (item 4, .PDF, 33 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40185043&FileExtension=.PDF&FileName=Record%20of%20Conversation%20Rotorway-Master.PDF - Rotorway Service Bulletin (item 5, .PDF, 43 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40185044&FileExtension=.PDF&FileName=Rotorway%20Service%20Bulletin-Master.PDF - TR Pulley System Diagram (item 6, .PDF, 73 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40185045&FileExtension=.PDF&FileName=TR%20Pulley%20System%20Diagram-Master.PDF - Photo 1. Aft Tail Rotor Drive Pulley (item 7, .PDF, 198 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40185046&FileExtension=.PDF&FileName=Photo%201.%20%20Aft%20Tail%20Rotor%20Drive%20Pulley-Master.PDF - Photo 2. Forward Tail Rotor Drive Pulley (item 8, .PDF, 222 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40185047&FileExtension=.PDF&FileName=Photo%202.%20%20Forward%20Tail%20Rotor%20Drive%20Pulley-Master.PDF From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.